A longitudinal study of maternal oxygen saturation during short-term submaximal exercise.

Purpose: Longitudinal prospective study before, during and after normal pregnancy of the effect of short-term submaximal exercise on maternal oxygen saturation.

Methods: Fourteen healthy women were recruited to the study before a planned pregnancy, and were followed seven times during the pregnancy and for up to 6 month after delivery. A submaximal bicycle exercise test with a target heart rate of 85% of the predicted age-adjusted maximum was performed. Maternal oxygen saturation was continuously recorded using a pulse oximeter.

Results: Maternal oxygen saturation at maximum work-load had increased significantly already at 8 weeks gestation compared with preconception levels, and remained at a significantly higher level until 29 weeks of gestation. Thereafter, the oxygen saturation continued to be higher even at 6 month postpartum. During the exercise test, the lowest saturation was found during the late recovery period, this remained unchanged before, during and after pregnancy.

Conclusion: A pregnant woman responds to short-term exercise by increasing the oxygen saturation until 29 weeks. After that, the saturation level decreases but remains at a higher level even 6 month after delivery compared with preconception levels.